Abstract-The rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons are located, is a central site via which angiotensin II (Ang II) elicits its pressor effect. We tested the hypothesis that NADPH oxidase-derived superoxide anion (O 2 ⅐Ϫ ) in the RVLM mediates Ang II-induced pressor response via activation of mitogen-activated protein kinase (MAPK) signaling pathways. Bilateral microinjection of Ang II into the RVLM resulted in an angiotensin subtype 1 (AT 1 ) receptor-dependent phosphorylation of p38 MAPK and extracellular signal-regulated protein kinase (ERK)1/2, but not stress-activated protein kinase/Jun N-terminal kinase (SAPK/JNK), in the ventrolateral medulla. The Ang II-induced p38 MAPK or ERK1/2 phosphorylation was attenuated by application into the RVLM of a NADPH oxidase inhibitor, diphenyleneiodonium chloride (DPI), an antisense oligonucleotide that targets against p22phox or p47phox subunit of NADPH oxidase mRNA, or the superoxide dismutase mimetic tempol. DPI or antisense p22phox or p47phox oligonucleotide treatment also attenuated the AT 1 receptor-dependent increase in O 2 ⅐Ϫ production in the ventrolateral medulla elicited by Ang II at the RVLM. Functionally, Ang II-elicited pressor response in the RVLM was attenuated by DPI, tempol, or a p38 MAPK inhibitor, SB203580. The AT 1 receptor-mediated enhancement of the frequency of glutamate-sensitive spontaneous excitatory postsynaptic currents induced by Ang II in RVLM neurons was also abolished by SB203580. These results suggest that NADPH oxidase-derived O 2 ⅐Ϫ underlies the activation of p38 MAPK or ERK1/2 by Ang II in the ventrolateral medulla. Furthermore, the p38 MAPK signaling pathway may mediate Ang II-induced pressor response via enhancement of presynaptic release of glutamate to RVLM neurons. (Circ Res. 2005;97:772-780.)Key Words: mitogen-activated protein kinases Ⅲ angiotensin II Ⅲ superoxide anion Ⅲ NADPH oxidase Ⅲ rostral ventrolateral medulla Ⅲ blood pressure I n addition to its well-known actions on the vasculature, angiotensin II (Ang II) also plays a critical role in central regulation of circulatory functions. 1,2 One brain target where Ang II exerts its influence on cardiovascular control is rostral ventrolateral medulla (RVLM), 3,4 where premotor neurons that maintain tonic sympathetic vasomotor outflow are located. 5 The RVLM contains a high density of Ang II receptors 6 and is a major site of the sympathoexcitatory and pressor actions of the octapeptide. 7,8 It is generally accepted that activation of Ang II type 1 (AT 1 ) receptors in the RVLM contributes mainly to the cardiovascular effects of Ang II. 9,10 The reactive oxygen species, particularly superoxide anion (O 2 ⅐Ϫ ), is an important intracellular messenger for brain Ang II. The octapeptide increases the activity of NADPH oxidase, the major source of O 2 ⅐Ϫ in the vasculature, 11 and enhances O 2 ⅐Ϫ production in the central nervous system. 12,13 Intracerebroventricular infusion of NADPH oxidase inhibitor antagonizes the increase in renal sympa...

Background-Overproduction of nitric oxide (NO) by inducible NO synthase (iNOS) in the rostral ventrolateral medulla (RVLM), where sympathetic premotor neurons are located, plays a pivotal role in the manifestation of fatal cardiovascular depression during endotoxemia. The iNOS gene is regulated transcriptionally by nuclear factor-B (NF-B) activation. The present study tested the hypothesis that heat shock protein 70 (HSP70) may confer protection against sepsis-induced circulatory fatality via inhibition of iNOS gene expression in the RVLM through prevention of NF-B activation. Methods and Results-Adult male Sprague-Dawley rats subjected to a brief hyperthermic heat shock (42°C for 15 minutes) exhibited significant upregulation of HSP70 in the RVLM. Brief heat shock preconditioning also significantly suppressed iNOS mRNA or protein surge and alleviated hypotension, bradycardia, and reduction in neurogenic sympathetic vasomotor activity manifested during experimental endotoxemia induced by intravenous administration of Escherichia coli lipopolysaccharide. An increase in DNA binding activity and nuclear translocation of transcription factor NF-B were detected during endotoxemia. Heat shock preconditioning significantly decreased DNA binding activity of NF-B, which was reversed by microinjection of an hsp70 antisense oligonucleotide bilaterally into the RVLM. Heat shock preconditioning also blocked inhibitory B (IB) kinase activity or degradation of IB in the RVLM during endotoxemia. Conclusions-We

Our results indicate that RSV, a major polyphenol found in red wine, exerts protection against acrolein-induced cytotoxicity in human ARPE-19 cells via increases in the mitochondrial bioenergetics. In addition, the antioxidant effect of RSV may contribute to protection against laser-induced CNV in animals exposed to CS. Therefore, RSV might be beneficial for treatment of acrolein-induced or CS-evoked RPE degeneration.

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Whereas induction of the 70-kDa heat shock protein (HSP70) in the nucleus tractus solitarii (NTS), the terminal site in the brain stem for primary baroreceptor afferents, augments baroreceptor reflex (BRR) response, the underlying cellular and molecular mechanism is essentially unexplored. In Sprague-Dawley rats, we evaluated the hypothesis that HSP70 may potentiate BRR response by up-regulating the molecular synthesis and functional expression of glutamate receptors in the NTS. Animals subjected to brief hyperthermic heat shock (HS; 42°C for 15 min) exhibited augmented expression of NR1 or NR2A subunit of N-methyl-D-aspartate (NMDA) receptors, GluR1 or GluR4 subunits of ␣-amino-3-hydroxy-5-methylisoxazole-4-propionate receptors and KA1 subunit of kainate receptors in the NTS. Intriguingly, this up-regulation of glutamate receptors was preceded by an increase in HSP70 expression at the NTS. The HS-induced augmentation in responsiveness of barosensitive NTS neurons to transient hypertension or potentiation of BRR response was discernibly blunted by MK-801 or 6-cyano-7-nitroquinoxaline-2,3-dione. Bilateral microinjection into the NTS of an antisense hsp70 oligonucleotide (50 pmol) before HS significantly suppressed the induced expression of HSP70 or the increase in glutamate receptor subunits in the dorsal medulla and discernibly attenuated the potentiation of BRR response. Control microinjection into the NTS of sense or scrambled hsp70 oligonucleotide (50 pmol) was ineffective. These findings suggest that HSP70 induced by HS may enhance BRR response by up-regulating the molecular synthesis and functional expression of NR1 or NR2A subunit of NMDA receptors and GluR1, GluR4, or KA1 subunit of non-NMDA receptors in the NTS.

Background-We demonstrated recently that heat shock (HS)-induced heat shock protein 70 (HSP70) expression in bilateral nucleus tractus solitarii (NTS), the terminal site in the brain stem for primary baroreceptor afferents, confers cardiovascular protection against heatstroke by potentiating baroreceptor reflex (BRR) response. This study evaluated the hypothesis that altered regulation of HSP70 expression may be associated with the heightened susceptibility to heatstroke during hypertension. Methods and Results-Spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto (WKY) rats anesthetized with propofol were used. Compared with WKY rats, significant induction in HSP70 or phosphorylation of heat shock factor 1 (HSF1), but not HSF2, in the NTS and potentiation of BRR response in SHR occurred earlier (4 versus 8 hours), reaching peak magnitude sooner (16 versus 24 hours), and declined more rapidly after a brief hyperthermic HS (42Ϯ0.5°C for 15 minutes). The protection conferred by HS against hypotension and bradycardia during the onset of heatstroke (45°C for 60 minutes), although effective, was less effective in SHR. Microinjection bilaterally into the NTS of the selective protein kinase A (PKA) inhibitor H-89 (100 pmol) or the selective PKC inhibitor calphostin C (100 pmol) significantly attenuated all of the above events induced in SHR by HS. However, only H-89 was effective in WKY rats. Conclusions-An

Activation of the arterial baroreceptors induces expression of the proto-oncogene c-fos in the nucleus tractus solitarii (NTS), the terminal site of baroreceptor afferents in the medulla oblongata. This induced expression is an intracellular event that is crucial to long-term maintenance of stable blood pressure. Using Sprague-Dawley rats maintained under propofol anesthesia, we evaluated the role and delineated the underlying molecular mechanisms of nitric oxide (NO) in this process. Baroreceptor activation induced by 30 min of sustained hypertension significantly and sequentially increased the level of cyclic GMP-dependent protein kinase I (PKG-I), phosphorylated cyclic AMP response element-binding protein (pCREB), c-fos mRNA, and Fos protein in the NTS. All of these upregulated expressions were significantly attenuated in animals that were pretreated immediately before baroreceptor activation with bilateral microinjection into the NTS of a selective neuronal nitric-oxide synthase (nNOS) inhibitor, 7-nitroindazole

Overproduction of nitric oxide (NO) by gene transduction of endothelial NO synthase (eNOS) in rostral ventrolateral medulla (RVLM), which is responsible for maintenance of vasomotor tone, reduces arterial pressure in spontaneously hypertensive rats (SHR). This NO-induced vasodepression, however, is not sustained and is followed by rebound hypertension. Because superoxide anion (O 2 . ) level is increased and synthesis or activity of mitochondrial manganese superoxide dismutase (SOD2) is reduced in RVLM during hypertension, we hypothesized that an interaction between NO and O 2 . in RVLM, using mitochondrial respiratory enzyme complexes (MRC) as the cellular target, contributes to those cardiovascular outcomes after eNOS gene transduction in SHR. The present study assessed this hypothesis using adenoviral vectors to overexpress eNOS (AdeNOS) and/or SOD2 (AdSOD2) in RVLM of SHR or normo- Nitric oxide (NO) is a gaseous molecule that plays an active role in central cardiovascular regulation (Zanzinger, 1999). One brain region in which NO is of pivotal importance in this regulatory machinery is the rostral ventrolateral medulla (RVLM) (Chan et al., 2001;Mayorov, 2005), which provides tonic sympathetic outflow for the maintenance of vasomotor tone (Dampney, 1994). Accumulating evidence suggests that NO deficiency in the RVLM may underlie sympathetic overexcitation (Kagiyama et al., 1998;Chan et al., 2003; TandaiHiruma et al., 2005) or impaired baroreflex regulation (Kishi et al., 2003) during hypertension. Accordingly, overproduction of NO by gene transduction of endothelial nitric-oxide